Mature Indian Wax Scale on Twig.
Photo: Matt Bertone, NC State University
Updated: August 16, 2022
Key points
Indian Wax Scale (Ceroplastes ceriferus) is a non-native type of soft scale insect and can be difficult to manage. Their waxy body covering shields them from predators and certain pesticides. Learn more about scale insect groups and biology on Introduction to Scale Insects.
This is a common pest of hollies and a range of shrubs and can cause leaf drop and dieback when populations are high.
Target monitoring and control efforts to the vulnerable crawler stage. Learn more about what to look for on Monitoring for Scale Insects.
Appearance
Mature female covers are rounded to hemispherical, white, and up to ¼” (6 mm) in diameter.
There are no males.
Crawlers are rusty-red.
Appearance of nymphs in “cameo” stage
Illustration: J.A. Davidson
Click image to enlarge
Nymph and mature scale comparison
Illustration: J.A. Davidson
Click image to enlarge
Appearance of adult Indian wax scale
Illustration: J.A. Davidson
Click image to enlarge
Common host plants
Sixty-two plant families are used by this species.
Evergreen shrubs, including Chinese holly (Ilex cornuta), Japanese holly (Ilex crentata), boxwood (Buxus), euonymus (Euonymus), firethorn (Pyracantha), and camellia (Camellia)
Deciduous shrubs, including spirea (Spiraea), flowering quince (Chaenomeles), and beautyberry (Callicarpa).
Where to look
All life stages will be found on twigs and small branches. Rarely, they can also be found on foliage.
Insects attracted to honeydew. Bees, wasps (including hornets), and ants exploring dense shrubs may indicate a wax scale population.
"Cameo” stage juveniles with adult on twig. Adults resemble a small wad of gum.
Photo: Brian Kunkel, University of Delaware, Bugwood.org
Plant damage
Light to moderate infestations will produce honeydew, which can attract other insects (mainly flies, wasps, and ants) and support the growth of sooty mold.
Heavy or prolonged infestations can cause leaf yellowing and shedding, and plants will lose vigor. Eventually, branch dieback occurs.
The crawler emergence period depends on temperature and can vary slightly from year to year. The approximate time to monitor for them is June.
They overwinter on the bark as adults.
Management
Refer to our general scale management recommendations for both chemical-based and pesticide-free options. When pesticides are warranted, a combination of dormant oil applications and the use of systemic or growth-regulating insecticides is the most effective approach. For large populations, scale suppression may require more than one year of intervention, and professional pesticide applicators will be needed to apply certain treatments.
The brief crawler emergence period for this species means that monitoring and treatment may need to occur in a relatively limited timeframe.
Just before the expected emergence period, start monitoring for crawlers. Since weather trends can shift date ranges, a more reliable prediction of timing can be made using Growing Degree Days and Plant Phenological Indicators. Here is a refined estimate of egg hatch and the beginning of crawler emergence:
1145 degree days
During the flowering of Bottlebrush Buckeye (Aesculus parviflora)
Before the flowering of Mimosa (Albizia julibrissin; invasive)
References:
Adapted from, Managing Insects and Mites on Woody Plants, authors: Ph.D. John A. Davidson, Ph.D.and Michael J. Raupp, Ph.D. The Pest Predictive Calendar, and Scale Crawler Emergence Period chart compiled by Stanton Gill, Suzanne Klick, and Sarah Kenney.
Complied by Miri Talabac, Horticulturist & Coordinator, HGIC 2022
